Class 8 Basic Science Chapter 3 Important Questions Kerala Syllabus Pressure

The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 3 Pressure Important Questions ensure conceptual clarity.

Pressure Extra Questions and Answers Class 8 Basic Science Chapter 3 Kerala Syllabus

Pressure Class 8 Important Questions

Question 1.
Which of the following is the unit of atmospheric pressure?
(N, parsec, kg/m³, bar)
Answer:
bar

Question 2.
It is possible to drink juice using a straw because of ……………………
Answer:
Atmospheric pressure

Question 3.
Correct the following. As the number of particles increases, gas pressure decreases.
Answer:
As the number of particles increases, gas pressure increases.

Question 4.
The instrument used to measure atmospheric pressure is a ………………………
Answer:
Barometer.

Question 5.
The pressure exerted on an area of 10 m² by a force of 50 N is ………………….. .
(5 N, 5 N/m², 0.2 N/m², 0.2 N)
Answer:
5 N/m²
P = F/A, F = 50 N, A =10 m²
P = 50 /10 = 5 N/m²

Question 6.
The instrument used to measure liquid pressure is ……………………. .
Answer:
Manometer

Question 7.
Choose the correct equation of pressure.
Answer:
(P = F × A, P = A/F, P = F/A)
Answer:
P = F/A

Question 8.
Observe the diagram

Water flowing down through the holes P, Q and R on a bottle is depicted.
a) Which is the correct figure? i/ii/iii
b) What is the reason for this inference?
Answer:
a) Figure iii is correct

b) As depth of liquid increases pressure increases. So the water flowing from the hole R will have the greatest force and covers more distance.

Question 9.
Observe the picture below. Both beakers contain the same volume of water.

a) Which beaker experiences maximum pressure at the bottom?
b) Justify your answer.
Answer:
a) Beaker A experience maximum pressure at the bottom.

b) The height of liquid column (or depth) is more in beaker A than beaker B. So more pressure is experienced at the bottom of beaker A.

Question 10.
Liquids also exert pressure. Write down any two factors that influence liquid pressure. (Term II, 2022)
Answer:

1. Height of the liquid column
2. Density of the liquid

Question 11.
The weight of the air column over unit area of earth’s surface is atmospheric pressure.
a) What is standard atmospheric pressure?
b) Name the instrument used to measure atmospheric pressure. (Annual 2022)
Answer:
a) Atmospheric pressure at sea level is known as standard atmospheric pressure. It is defined as the weight of a mercury column that is 0.76 m high, with a unit cross sectional area, exerting a pressure of 1 atm.

b) Barometer.

Question 12.
Two identical balloons one filled with water and other with kerosene of equal quantity.

a) Identify the balloon filled with water.
b) Why is the expansion of balloons appear different in figures (a) and (b)? (Annual 2022)
Answer:
a) Figure (b)

b) Water has higher density than kerosene. As density increases, liquid pressure increases. So the balloon which is expanded has water filled in it and the other balloon which is small in size has kerosene filled in it.

Question 13.
Check whether the given statement is correct or wrong. Correct the wrong statement.
(i) Atmospheric pressure increases as height from the Earth’s surface increases.
(ii) The porters in railway stations place a piece of cloth before carrying luggage on head to decrease the area of contact between luggage and head to reduce the pressure felt on their head.
Answer:
(i) Statement is wrong
Corrected statement: Atmospheric pressure decreases as height from the Earth’s surface increases.

(ii) Statement is wrong
Corrected statement: The porters in railway stations place a piece of cloth to increase the area of contact between luggage and head to reduce the pressure felt on their head.

Question 14.
Calculate the force exerted by atmospheric pressure on a table surface of area 3 m². Atmospheric pressure is 101325 Pascal.
Answer:
Force = Pressure × Area
= 1 Pa × 3 m² = 101325 × 3
= 303975 N

Question 15.
The thrust acting per unit area by a liquid is the liquid pressure.

a) Three points A, B and C are marked on a cylindrical glass vessel filled with water as shown in figure. If three identical inflated balloons are placed on these points inside the cylinder, which one will be the largest in size? Justify your answer.
b) Do you expect any change in size to the balloons, if the water is replaced with kerosene? Explain.
Answer:
a) The balloon placed in the position A will be the largest in size. As depth decreases liquid pressure also decreases. The pressure experienced at position A is the least compared to positions B and C and so the balloon with largest size occupies position A.

b) Yes, when kerosene is replaced with water the size of the balloons become comparatively larger than in water because kerosene has low density than water. When density decreases liquid pressure also decreases. So when the pressure experienced is less, the size of balloons (volume of balloons) is comparitively larger.

Question 16.
When area increases, pressure decreases. Find three situations where this principle is applied.
Answer:
a) We can walk easily through a muddy place by placing a plank over it.
b) Ducks walk easily over mud.
c) Constructing dams with wider basements.

Question 17.
Write down reasons for the following statements.
a) Astronauts wear specially designed suits.
b) Sewing needles are made with sharp tips.
c) Connecting the wheels of tanks and other such vehicles using wide chains.
Answer:
a) The suit helps us to maintain the pressure between the dress and the body equal to the atmospheric pressure.

b) Sharp tips have less surface area of contact. As area of contact decreases, pressure increases so that sewing needles can pierce into the materials to be stitched easily.

c) Connecting wheels of tanks and other such vehicles using wide chains helps in making more surface area of contact with the ground to exert less pressure over it. This ensures its smooth motion.